The autofill on my Liberty is either a Headhunter or a Headhunter modified by Liberty. With the switch set to auto the pump takes the water tank down to 20% at which time the auto fill feature opens the solenoid valve and at 80% the valve closes.

On our Libertys (Jim's and mine and others) we can use municipal water and not draw from our tank or use the pump, but the pump we are equipped with delivers a very high flow of water so we can be using multiple sources of water and there is no reduction in flow. We are not assured of ample flow on a municipal supply.

So our tanks, even when on autofill can have as much as 80% capacity, or as little as 21% capacity. When I fill manually I always dump the holding tank so I am also assured I will never have an issue with an over full tank. If I rely on autofill there is not that assurance and we are then relying on the Headhunter tank ,monitor warning us of a full tank condition. I would rather avoid what could occur if the sensor system should fail by just doing things manually because there is no automatic dumping feature for the holding tank, although we can dump via the air operated valve or macerator without stepping outside the coach.